Fichas
Asymmetric Encryption
Fichas del conjunto (15)
- 1Briefly describe Public-key EncryptionTwo keys, one public one private.
Infeasible to calculate private key from a public key.
Security achieved through intractable mathematical problems. - 2What is Public-key Encryption used for?Symmetric key exchange and sender verification
- 35 differences between symmetric and asymmetric encryption1 vs 2 key.
Small vs large key size.
Fast vs slow.
Long term comms vs key exchange / verification.
SP Networks vs Mathematical problems - 4State the 3 mathematical principles used in asymmetric cryptology- Large (typically prime) numbers
- Modular arithmetic
- Integer factorisation - 5What is the congruence relation?a === b (mod n) => a (mod n) = b (mod n)
- 6Give the eqivalences of modular arithmetic((a mod n) + (b mod n)) mod n = (a + b) mod n
- 7What is a discrete logarithm? Draw the expressionCombining logs with modular arithmetic. Hard to compute and requires brute force.
- 8What is a primitive root?A generator for a prime P which, when raised to an exponent and modular P, produces all values between 0 and P-1
- 9What is DHKEX?Diffie-Hellman Key Exchange.
Exchanges symmetric keys in private using discrete logarithms. - 10Describe the 5 steps of DHKEX
- 11Why is DHKEX secure? Draw equation to be solvedSymmetric key g^ab can only be solved by knowing either private exponents, a or b.
- 12What is DHKEX vulnerable to?Man-in-the-middle attacks. Intercept initial comms and create two separate key exchanges between A and B.
- 13Describe the Logjam attack.512-bit DH attack.
Number field sieve to precompute 3/4 stages of DH for a given prime.
Final stage computed at attack time. Works since same primes are often used (Oakley Group 2) - 14What is PFS?Perfect forward secrecy.
Establish a new symmetric key each session.
Known as Ephemeral Mode in practice. - 15What is Elliptic Curve?An alternative to modular arithmetic and discrete logs.
Uses a curve to decide key in the form of y^2 = x^3 + ax + b.
Stronger than other methods for the same key size
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- Descripción
- Bachelors Degree (Computer Security) Computer Science Fichas sobre Asymmetric Encryption, creado por Alex Neves el 21/05/2016.
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- Alex Neves
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